'''#判断是否为奇数
num=int(input("输入一个数:"))

print(f"num={num}")

if num%2==0:
    print("非")
else:
    print("是")'''

'''#判断闰年
year=1
while year>0:
    year = int(input("请输入:"))
    if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0 and year % 100 == 0):
         # print(True)
         pass
    else:
         print(False)

'''
'''i=0
while i<=10:
    print(i)
    i+=1'''

'''i=add=0
while i<=100:
    if i%2==0:#若果i非奇数
        add=add+i
        print(add)
    i += 1


print(add)'''

'''for i in range(0,11):
    print(i)'''

'''for i in range(0,11,5):
    print(i)
'''

'''for i in range(0,11,1):
    if i==3:
        continue
    print(i)

for i in range(0,11,1):
    if i==3:
        break
    print(i)'''

i=0
add=0
while True:

    if i==30:
        break

    add=add+i
    i+=1

print(add/i)